Fig. 5. A C-terminal valine mediates transport of a signalless reporter to the cell surface. The localization of oligomeric and monomeric ERGIC-53 constructs with and without a valine transport signal was analyzed by immunofluorescence microscopy. COS cells were transfected with oligomeric (A to F) or monomeric (G to L) constructs L53L₁₈R₂S₁₀ (D to F, J to L) or L53L₁₈R₂S₉V (A to C, G to I) and processed for immunofluorescence microscopy 20 hours later. Panels A, D, G and J (bar, 50 µm): surface labeling of nonpermeabilized cells. Other panels: double staining after permeabilization (bar, 25 µm). Panels A, B, D, E, G, H, J and K: staining with anti-myc. Panels C, F, I and L: staining with a mAb against the ER marker BAP31.